Background: We measured C-reactive protein (CRP), a clinical marker of systemic inflammation, in maternal serum collected at 13 weeks gestation on average, to determine whether elevations precede the clinical manifestation of preeclampsia.
Methods: Using a prospective, nested, case-control study design we measured CRP concentrations using a competitive immunoassay in 60 women who developed preeclampsia and in 506 women who remained normotensive throughout pregnancy. Logistic regression procedures were used to calculate odds ratio (OR) and 95% CI. Because maternal serum CRP is highly correlated with maternal prepregnancy body mass index (BMI), all analyses were repeated after stratification by maternal prepregnancy overweight status (BMI <25 v > or =25 kg/m(2)).
Results: Overall, the risk of preeclampsia increased across successively higher tertiles of CRP (OR = 1.0, 1.6, and 3.5, with the lowest tertile as the referent group; P <.001 for trend). After adjusting for parity and first-degree family history of chronic hypertension, the OR in the highest tertile was 3.2 (95% CI = 1.5 to 6.7). Further adjustment for BMI greatly attenuated this association (OR = 1.8, 95% CI = 0.8 to 4.1). Elevated CRP concentrations (> or =4.9 mg/L) were associated with a 2.5-fold increased risk of preeclampsia (95% CI = 1.1 to 5.5) in lean women. No similar association was observed among overweight women.
Conclusions: Elevated CRP is highly correlated with prepregnancy adiposity and appears to be an independent predictor of preeclampsia in lean women. Further work is needed to identify modifiable risk factors for systemic inflammation in early pregnancy and to explore further the extent to which CRP and prepregnancy adiposity independently and jointly contribute to preeclampsia risk.